Journal
RESOURCES CONSERVATION AND RECYCLING
Volume 186, Issue -, Pages -Publisher
ELSEVIER
DOI: 10.1016/j.resconrec.2022.106556
Keywords
WasteNa(2)SO(4); Bipolar membrane electrodialysis (BMED); Recycling; Waste management
Categories
Funding
- National Natural Science Joint Foundation of China-Sri Lanka [RCEES-TDZ-2021-32, 218611422020]
- State Key Joint Laboratory of Environment Simulation and Pollution Control (Research Center for Eco-environmental Sciences, Chinese Academy of Sciences) [21Z01ESPCR]
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In this study, a BMED-5 system was established to simultaneously produce (NH4)2SO4, HCl, and NaOH from waste Na2SO4. The optimization of energy efficiency and conversion ratio of the BMED-5 system was investigated, and high product concentrations and conversion ratios were achieved.
Na2SO4 is generated during zero-liquid discharge treatment of high-salinity wastewater and is of limited in-dustrial use. In this study, a five-compartment bipolar membrane electrodialysis metathesis (BMED-5) system was established to produce (NH4)(2)SO4, HCl, and NaOH simultaneously from waste Na2SO4 by adding an equivalent amount of NH4Cl. The conditions for optimizing the performance of the BMED-5 system in terms of its energy efficiency and conversion ratio were investigated. The inflection point of the stack voltage occurred at a final Na2SO4 concentration of 0.03 mol/L, corresponding to a conductivity of approximately 6 mS/cm in the Na2SO4 compartment, which could be considered the end point of the reaction. In comparison with the widely used three-compartment bipolar membrane electrodialysis (BMED) system, which could convert the waste salts into an acid and a base, the BMED-5 system in study only consumed a little higher energy to produce three products. The highest (NH4)(2)SO4 (0.44 mol/L), HCl (1.03 mol/L), and NaOH (1.35 mol/L) concentrations were obtained with an initial Na2SO4 concentration of 0.8 mol/L and a current density of 40 mA/cm(2), yielding a conversion ratio of up to 96% and energy consumption of 2.961 kWh/kg Na2SO4. The gross profit and payback period of BMED-5 were estimated to be 178.4 $/t Na2SO4 and 2.3 years, respectively.
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